Local populations in marginal habitats close to the distribution border are expected to vary more in size than central populations. To obtain information on the viability of metapopulations, monitoring in peripheral habitats might therefore be an effective way. To test this hypothesis we analysed breeding success and fluctuations in population size of Pied Flycatcher Ficedula hypoleuca in three subalpine forests in Scandinavia, each representing a peripheral habitat (in southern Norway, Hemsedal, in central Norway, Lierne, and in northern Sweden, Ammarnäs). Data were collected in the period 1986–2005. Numbers of flycatchers in these peripheral habitats in Fennoscandia have been increasing for decades, but since the 1970s negative trends are observed. This study showed that the populations breeding in Lierne and Ammarnäs exhibited demographic characteristics that are typical for sink populations, i.e. large annual variation in recruitment, which was on average insufficient to maintain population size; in contrast Hemsedal seemed to function as a source population. The decrease in population size since the start of this survey was most evident for the two sink populations. Weather conditions at the flycatcher’s wintering areas in western Africa were suspected to be responsible for the decrease, at least there were no indications of any climatic change at the breeding grounds. However, breeding success of the sink populations was significantly correlated to June temperatures. During the last years of the study, all three populations seemed to recover. This recovery was most pronounced for the source population in Hemsedal while the other two populations showed some time-lag. As an index of the Fennoscandian population size of Pied Flycatcher we used catch data in autumn from three ringing stations in southern Scandinavia. The numbers of initiated clutches in our populations were correlated with this index from the previous autumn, supporting the idea that populations in peripheral habitats are sensitive yardsticks for overall population size. Similarly, the numbers of successful clutches in our two populations with low predation rate were positively related to the same index. Taken together, our three border populations are considered good indicators for the overall population trend in Fennoscandia.